Analysis of 25 patients who fulfilled clinical and radiographic criteria for the diagnosis of "normal pressure" hydrocephalus (NPH) demonstrated (1) a significant relationship between presence of motor signs with good outcome and absence of motor signs with poor outcome following ventricular shunting, (2) symptoms and signs of parkinsonism in 40% of patients in whom the diagnosis of NPH was made, and (3) no reliable relationship between radiographic measurements or cisternogram appearance and outcome following shunting. The clinical picture is the most important factor in selection of NPH patients for surgery.